Pin Me

Genetics of McCune-Albright Syndrome

written by: R. Elizabeth C. Kitchen•edited by: Emma Lloyd•updated: 6/30/2010

If you or someone you know is affected by McCune-Albright syndrome, it is important to fully understand this disorder. Read on to learn more about this disorder and the genetics involved.

  • slide 1 of 8

    The genetic disorder McCune-Albright syndrome affects the color of the skin (pigmentation) and the bones. This genetic disorder is much different than most because it is not inherited.

  • slide 2 of 8

    How Common is this Genetic Disorder?

    McCune-Albright syndrome affects about one in 100,000 to one in one-million people throughout the world.

  • slide 3 of 8

    Genetics of McCune-Albright Syndrome

    McCune-Albright Syndrome This disorder is not passed to child to parent like most genetic disorders. It occurs when the DNA is mutated within the womb as the baby is developing. The gene associated with this disorder is the GNAS1 gene.

  • slide 4 of 8

    Symptoms of McCune-Albright Syndrome

    The hallmark symptom of this disorder is premature puberty in girls. In normal girls, they will develop pubic hair and breasts before starting their menstrual cycle, however, girls with McCune-Albright syndrome can begin their menstrual cycle during their early childhood years, long before they develop pubic hair and breasts. Menstrual bleeding and puberty can start as early as four to six months. Boys may also experience early sexual development, but not nearly as commonly as girls do.

    Other symptoms can include:

    • Bone fractures
    • Gigantism
    • Deformities in facial bones
    • Large, irregular patchy spots referred to as cafe-au-lait spots, specifically affecting the back

    Complications are also possible with this disorder. They can include:

    • Blindness
    • Deafness
    • Premature puberty
    • Repeated broken bones
    • Bone abnormality-related cosmetic problems
    • Osteitis fibrose cystica
    • Tumors
  • slide 5 of 8

    Diagnosing this Genetic Disorder

    When diagnosing this condition, the doctor will begin with a physical exam, specifically looking for signs of:

    • Abnormal skull bone growth
    • Acromegaly
    • Gigantism
    • Hyperthyroidism
    • Large cafe-au-lait spots present on the patient's skin
    • Ovarian cysts
    • Scar-like tissue within bone
    • Abnormal heart rhythms
    • Adrenal abnormalities
    • Hyperparathyroidism
    • Hypophosphatemia
    • Liver disease, fatty liver, jaundice
    • Thyroid or pituitary tumors

    Blood tests can be done too test for high levels of certain hormones including:

    • Adrenal hormones
    • Growth hormone
    • Blood prolactin

    Other diagnostic testing can include:

    • MRI of the head
    • X-rays of the bones
    • Genetic testing to determine if the GNAS1 gene is mutated
  • slide 6 of 8

    How is McCune-Albright Syndrome Treated?

    There is no specific treatment regimen available to treat this condition. Certain drugs, such as testolactone, that block estrogen production have been tried and have shown some success and promise. Surgery to remove the adrenal glands can sometimes be done to treat adrenal abnormalities. Pituitary adenoma and gigantism will have to be treated with surgery or with drugs referred to as hormone inhibitors.

    Those with this condition often have a relatively normal lifespan. However, they will need to keep all necessary doctors appointments so that their doctors can keep and eye on their condition and make any treatment changes as they become necessary.

  • slide 7 of 8

    Resources

    Medline Plus. (2008). McCune-Albright Syndrome. Retrieved on June 24, 2010 from Medline Plus: http://www.nlm.nih.gov/medlineplus/ency/article/001217.htm

    Genetics Home Reference. (2009). McCune-Albright Syndrome. Retrieved on June 24, 2010 from Genetics Home Reference: http://ghr.nlm.nih.gov/condition/mccune-albright-syndrome

  • slide 8 of 8

    Image Credits

    DNA: svilen001 – sxc.hu